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Re: cubic root [message #83964 is a reply to message #68737]

Tue, 16 April 2013 08:19

Lajos Foldy
Messages: 176
Registered: December 2011

Senior Member

On Tuesday, April 16, 2013 5:08:12 PM UTC+2, fd_...@mail.com wrote:
> Hi all
>
>
>
> I have a question about cubic roots. The cubic roots of a negative number there exists. The cubir root of -1 is -1, 0f -2 is -1.25 and so on why when I typed in IDL to calculate the cubic root of a negative value it print out NaN which means Not a Number?
>
>
>
> E.g. I typed: (-1)^1.0/3 and it prints out NaN
>
>
>
> Is there any way to fixed it and don't get NaNs but get the actual value?
>
>
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> Best Wishes
>
> Maria

(-1)^1.0/3 gives -0.333333 for me.

You have to specify that you want complex roots:

IDL> help, complex(-1.0)^(1.0/3)
<Expression> COMPLEX = ( 0.500000, 0.866025)

(and note that ^ has higher precedence than /).

regards,
Lajos

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[Message index]

		Cubic root finding on a grid By: Luds on Fri, 20 November 2009 08:03
		Re: cubic root By: Lajos Foldy on Tue, 16 April 2013 09:44
		Re: cubic root By: wlandsman on Tue, 16 April 2013 08:27
		Re: cubic root By: Lajos Foldy on Tue, 16 April 2013 08:19

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